In recent years, a density of heat generation from a heat generating component has rapidly increased with high performance of electronic apparatuses such as smart phones, tablets and notebook computers. Therefore, heat diffusion technologies have been imperative for such electronic apparatuses.
In particular, small-sized mobile apparatuses often come into direct contact with the human body, and temperature elevation outside their housings has become a serious problem. As one problem caused from such temperature elevation of outer surfaces of housings of mobile apparatuses, low-temperature burn injuries can be mentioned. Low-temperature burn injuries are a type of burn injury caused from long-term exposure of the human body to a temperature higher than the body temperature. There has been a report that a burn injury can be caused from the exposure at 44° C. for 6 hours, and that an increase of the temperature by 1° C. reduces the time required to cause the burn injury by half. Compared with usual burn injuries, in most cases of low temperature burn injuries, persons are late in being aware of progression of the symptoms, and there are often cases where their skins are seriously damaged when they are aware of the progression.
Moreover, liquid crystal displays or organic EL displays are used for display devices in mobile apparatuses. However, these display devices are susceptible to heat. When heat generated from heat generating components is transferred to these display devices, such heat transfer becomes a factor causing uneven brightness and deterioration in the shelf life of displays. Therefore, in order to achieve both high performance and size/thickness reduction of mobile apparatuses, it is required that heat transfer to display devices be effectively reduced.
Furthermore, recently, there are many cases where low-temperature burn injuries are caused when small-sized notebook computers are used on the knee for long time. Because miniaturization or mobilization of apparatuses will increasingly proceed in the future, it is very important to suppress the surface temperature of apparatuses as low as possible, even by 1° C.
Meanwhile, as a method for preventing an increase in the surface temperature of an apparatus, use of a heat insulation member can be considered in order to prevent heat from a heat generating component inside a housing of an apparatus from transmitting to the housing.
For example, with regard to a composite material with a conventional laminate structure shown in FIG. 4, use of a composite material with a laminate structure such as an adhesive layer 405/heat conductive layer 404/adhesive layer 403/heat insulation layer 402/adhesive layer 401 has been considered in the direction from a heat insulation component 406 to a housing 407, in order to prevent heat from the heat generating component 406 inside the housing of the apparatus from transmitting to the housing 407. Furthermore, a metal sheet, a graphite sheet and the like for the heat conductive layer 404; and a resin sheet (e.g., unwoven fabric or resin sheet) that contains capsules such as glass beads including the air, for the heat insulation layer 402, have been studied.
According to the above technology, there has been an attempt to homogenize a temperature distribution inside the housing 407 by reducing the heat transfer to the housing 407 (JP-A-2012-504484)